Fastest simple key-value store, multiple writers, like Redis?

Hi,

I'm working on a project with multiple different data storage backends. I'd
like to consolidate and use Postgres for more things. In one new situation
we're starting to use Redis, thinking it will perform better than Postgres
for a table that is updated a lot by concurrent background jobs.

I'm skeptical of no-sql stuff for various reasons. I'm wondering what PG
experts think -- is there is a way to configure Postgres to handle a table
differently, so that it could compete with Redis? Or are there some
workloads where it is definitely better to use an alternative data store?

This table will have a few million rows, five small columns. Rows will be
updated, read, or inserted 5-10 million times a day, by concurrent
processes. It operates like a key-value store in that most selects will be
getting one row, and maybe updating that row. Ideally these processes could
work without stepping on each other's toes and competing for locks.

Rob